High-temperature resistant copolymer oil well cement retarder: Synthesis, assessment of performance, and mechanism of retardation
This work used aqueous solution free radical polymerization to create polymers of 2-acrylamide-2-methylpropane sulfonic acid, itaconic acid, and allyl polyoxyethylene ether as a high-temperature resistant retarder (APMS/IA/APEG, from now on referred to as AIA). Gel permeation chromatography, fourier transform infrared (FTIR), proton nuclear magnetic resonance ( 1 HNMR), and thermo-gravimetric analysis (TG) were used to characterize their molecular structure and characteristics. Tests were conducted on the thickening time, rheological characteristics, and compressive strength of AIA in cement slurries. The cement slurry thickened for 276 min at 180°C during the test, and the cement stone's 24-h compressive strength was consistently more than 20 MPa. The hydration products were analyzed using x-ray diffractometer and scanning electron microscopy methods, which were then coupled with molecular dynamics simulations to elucidate the AIA retarding mechanism. When AIA is added to a cement slurry, it forms a chelate structure with Ca 2+ and a strong adsorption layer on the surfaces of the cement particles. This stops the cement from hydrating. The AIA side chain, APEG, can wrap the active group in AIA at low temperatures. AIA exposes more adsorption groups because of the APEG chains stretching at higher temperatures. AIA can, therefore, be used for deep well operations at high temperatures.
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